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Mechanical and Microstructural Properties of Native Pediatric Posterior Cruciate and Collateral Ligaments
Elaine C Schmidt1, Matthew Chin1, Julien T Aoyama2
1Biedermann Laboratory for Orthopaedic Research, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Insights
Pediatric medial collateral (MCL) and lateral collateral (LCL) ligaments show similar mechanical properties, while the posterior cruciate ligament (PCL) is weaker. These pediatric knee ligaments are less robust than adult counterparts, requiring further research for optimal injury treatment.
Area of Science:
- Orthopedics
- Biomechanics
- Pediatric Sports Medicine
Background:
- Medial collateral ligament (MCL) injuries are common, yet pediatric data is scarce.
- Lateral collateral ligament (LCL) and posterior cruciate ligament (PCL) injuries occur less frequently but are significant in multiligament trauma.
- Lack of information on native pediatric ligament properties hinders effective treatment optimization.
Purpose of the Study:
- To characterize the mechanical and microstructural properties of pediatric MCL, LCL, and PCL.
- Utilize a rare cohort of pediatric cadaveric knee specimens (mean age, 9.2 years).
Main Methods:
- Descriptive laboratory study involving tensile loading of harvested pediatric knee ligaments (MCL, LCL, PCL).
- Microstructural analysis using bright-field, polarized light, and transmission electron microscopy to assess collagen fiber morphology.
- Utilized 5 fresh-frozen pediatric knee specimens (3 male, 2 female).
Main Results:
- Pediatric MCL and LCL demonstrated similar ultimate stress, strain, and Young's modulus.
- Pediatric PCL exhibited lower ultimate stress and Young's modulus but higher ultimate strain compared to MCL and LCL.
- All three pediatric ligaments had comparable crimp wavelengths and collagen fibril diameters, but varied fibril distribution profiles.
Conclusions:
- Pediatric MCL and LCL possess similar mechanical profiles; PCL is weaker but more extensible.
- Pediatric collateral and posterior cruciate ligaments are biomechanically weaker than their adult counterparts.
- These findings provide preliminary data crucial for future pediatric knee ligament research and clinical practice.
Background:
Although anterior cruciate ligament (ACL) tears have received the most attention, the medial collateral ligament (MCL) is thought to be the most commonly injured knee ligament overall. The lateral collateral ligament (LCL) and posterior collateral ligament (PCL) are less frequently compromised but can be involved in severe multiligament injuries. The paucity of information on the native properties of these ligaments in the pediatric population hinders the overall optimization of treatment for these injuries.
Purpose:
To characterize the mechanical and microstructural properties of pediatric MCLs, LCLs, and PCLs using a rare cadaveric cohort (mean age, 9.2 years).
Study Design:
Descriptive laboratory study.
Methods:
MCLs, LCLs, and PCLs were harvested from 5 fresh-frozen pediatric knee specimens (3 male, 2 female) and were subjected to a tensile loading protocol. A subset of contralateral tissues from a single donor was analyzed using bright-field, polarized light, and transmission electron microscopy to measure collagen fiber morphology.
Results:
The pediatric MCL exhibited values for ultimate stress (11.7 ± 6.7 MPa), ultimate strain (18.2% ± 6.8%), and the Young modulus (93.7 ± 56.5 MPa) that were similar to values for the LCL (11.4 ± 11.5 MPa, 27.7% ± 12.9%, and 64.4 ± 76.6 MPa, respectively). The PCL demonstrated decreased ultimate stress (4.2 ± 1.8 MPa), increased ultimate strain (28.8% ± 11.9%), and a decreased Young modulus (19.8 ± 10.4 MPa) when compared with the MCL and LCL. All 3 ligaments had similar mean crimp wavelengths (MCL, 32.8 ± 3.6 µm; LCL, 27.2 ± 3.5 µm; PCL, 25.8 ± 3.5 µm) and collagen fibril diameters (MCL, 88.0 ± 26.0 nm; LCL, 93.3 ± 34.6 nm; PCL, 90.9 ± 34.0 nm); however, the fibril distribution profiles exhibited different modalities.
Conclusion:
The pediatric MCL and LCL possessed similar mechanical properties, while the pediatric PCL was weaker but capable of withstanding higher amounts of strain. All 3 of these pediatric structures were weaker than what has been reported in studies with adult cohorts.
Clinical Relevance:
Results from this study can be considered preliminary mechanical and microstructural data for healthy pediatric collateral and posterior cruciate ligaments that can be used to guide further laboratory and clinical research.
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